The present invention relates to a semiconductor integrated circuit device and to a power distribution bus for a semiconductor integrated circuit device.
In the semiconductor art, there has been a substantial increase in processing yields in recent years due to increased understanding and control of the various processes necessary to form semiconductor devices. This has lead to increasingly more complex semiconductor integrated circuit devices and indeed at the present time it is not unusual for an individual semiconductor chip to contain well over 12,000 semiconductor devices.
It can be expected that in the not too distant future, attempts will be made to manufacture even more complex circuits. Essentially this is because the manufacture of many thousands of devices is just as cheap as the manufacture of one from a processing point of view. It is anticipated that soon the major component of the cost of an integrated circuit will be the packaging cost. Therefore intense efforts are being made to package more and more semiconductor devices into a single package.
Thus it has been proposed that instead of using individual chips of semiconductor material (for example 5 mm square) mounted in a package, use is made of a complete wafer of semiconductor material (for example from 25 to 75 mm in diameter). Such an approach could indeed save much of the packaging cost if process yields can be satisfactorily maintained. Co-pending U.S. application Ser. No. 367,093, filed June 4, 1973 in the name of Joseph C. Logue for "Method of Manufacturing Multi-Function LSI Wafers", and assigned to the present assignee describes a large scale integrated circuit in which, during manufacture two sets of wafers are produced, one being the mirror image of the other. The wafers are divided into two groups, one that has "mainly good" circuits and the other with "mainly bad" circuits. If a circuit in a wafer of the "mainly good" set is defective, it is electrically isolated and a mirror image replacement circuit from a "mainly bad" set is mounted over it. Because it is a mirror image, the input/output pads of the "flipped" replacement circuit coincide with the input/output pads of the isolated defective circuit.
One major problem associated with packaging a semiconductor wafer, which may contain a complete data processor, is the power distribution within the wafer. Generally, although conductive paths formed on or in the surface of the wafer are adequate as conductors for signals, they can in some circumstances have the inadequate thickness or width for carrying power to the various devices formed in the wafer.